Astronomers are not sure why HVGC-1 was exiled from M87. One theory suggests that gravitational interactions with a pair of supermassive black holes at the galaxy’s center could have kicked out the cluster. Most galaxies contain a single giant black hole. If M87 is the product of a merger of two galaxies, it might host two central black holes in a binary system, researchers say.

In fact, that same double black hole future might await the Milky Way when we collide with our neighboring galaxy, Andromeda, in a few billion years. At which point, some star cluster may find itself ejected from the Milky Way, just like the ostracized HVGC-1.

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